Apex domains cannot have CNAME records.
Question and response
Question
dig CHARTER.COM. NS
Answer
CHARTER.COM. 2 NS ns2.CHARTER.COM.
CHARTER.COM. 2 NS ns1.CHARTER.COM.
CHARTER.COM. 2 NS ns4.CHARTER.COM.
CHARTER.COM. 2 NS ns3.CHARTER.COM.
Authority
The response has no authority records.
Additional
ns1.charter.com. 2 A 24.216.90.1
ns2.charter.com. 2 A 24.216.90.2
ns3.charter.com. 2 A 24.240.146.1
ns4.charter.com. 2 A 24.240.146.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0